Field of the Invention
Exemplary embodiments of the present invention relate to an exhaust heat regenerator for a vehicle, and more particularly, an exhaust heat regenerator for a vehicle which is able to collect exhaust heat using coolant, store in a heat accumulator, and use the exhaust heat stored in the heat accumulator, during a cold start operation or for heating a passenger compartment.
Description of the Related Art
Engines for vehicles are a power generation apparatus for a vehicle which converts thermal energy generated by burning fuel into kinetic energy and transmits the kinetic energy to wheels through a drive line, thus enabling the vehicle to drive.
However, energy used to drive the vehicle is only portion of the entire generated energy. Most of the generated energy is released and lost into the air in a form of thermal energy through the surfaces of an engine and an exhaust system or by discharge of exhaust gas.
In particular, there is a large energy loss due to discharge of high-temperature exhaust gas. Given that, an exhaust heat recovery system (EHRS) has been introduced, which collects some of exhaust heat and uses it to heat a passenger compartment.
As shown in FIG. 1, a conventional exhaust heat recovery apparatus includes a heat exchanger 3 which is installed to enclose a circumferential surface of an exhaust pipe 2, and a coolant pipe 5 which circulates through the engine 1, the heat exchanger 3, and a passenger compartment heater 4.
Coolant discharged from the engine 1 passes through the heat exchanger 3 installed on the exhaust pipe 2 and thus absorbs heat from exhaust gas so that it is heated. Subsequently, when passing through the heater 4, the coolant heats air which is supplied into the passenger compartment, thus heating the passenger compartment. That is, heat of exhaust gas, which has been discharged from the engine 1 and then directly exhausted to the air through the exhaust pipe 2 in the existing technique, can be collected and used to heat the passenger compartment, whereby energy use efficiency can be improved.
Representative examples of the exhaust heat recovery apparatus which uses coolant to collect exhaust heat were proposed in Korean Patent Unexamined Publication No. 10-2012-0080867 (filed by Korea Automotive Technology Institute, and entitled “APPARATUS FOR PREHEATING COOLANT USING EXHAUST HEAT”), and in Korean Patent Unexamined Publication No. 10-2012-0133487 (filed by Dgenx Co, Ltd./Kongju National University Industry-University Cooperation Foundation, and entitled “EXHAUST HEAT RECOVERY APPARATUS FOR VEHICLE).
However, in the conventional exhaust heat recovery apparatuses, immediately after an engine starts, that is, when the temperatures of exhaust gas and the exhaust pipe 2 are not increased to a sufficient degree, an increment in the temperature of coolant is small. Thus, there is little effect on improvement in engine warm-up performance.
Furthermore, the conventional exhaust heat recovery apparatuses are problematic in that it is impossible to heat a passenger compartment immediately after the engine starts in the winter because of the above-mentioned reasons.
Moreover, a heat accumulator which is installed in the conventional exhaust heat recovery apparatuses can neither absorb a large amount of heat nor store it for a long time due to low heat exchange performance and heat accumulation performance.